I want to stress that we need to have a relatively concrete list of problems the changes are meant to address which will help us develop the questions we want to ask which will help us design a schema for collecting the data that answers those questions.

Here's what I've got written so far:

changes are meant to decrease the bounce rate

changes are meant to reduce time spent on the portal

There was a third one that Moiz mentioned that I couldn't quite catch.

Something analogous to accept_language. If it largely agrees with what wiki they end up with, that points to there being some advantage in automagically changing what links we give people based on their browser's language settings.